The invention relates to surface-modifying a thermal barrier assembly.
Metal exterior window and door casings, which are often made of aluminum, are widely used in a variety of structures including office and industrial buildings. Such metal casings are good thermal conductors and therefore can cause considerable heat loss in winter and heat gain in summer in buildings in which they are installed. To reduce this problem it is common to employ a “thermal barrier” between the interior and the exterior portions of a metal casing. The thermal barrier often includes a material of relatively low thermal conductivity, which serves to interrupt the transfer of thermal energy between the interior and exterior metal portions.
Thermal barriers often consist of a channel defined by two structural components, e.g., metal segments and an adhesive composition disposed in the channel.
Thermal barriers, when part of a structure such as a building, are often subjected to high stresses caused by day, night and seasonal thermal cycling of the metal segments, which have much lower thermal expansion coefficients than the composition disposed in the channel of the thermal barrier. These stresses are different on each side of the thermal barrier due to the differential between the interior and exterior temperatures. Consequently, the adhesive composition may bond from the metal segments of the thermal barrier resulting in a loss of structural integrity, which can lead to gaps and water infiltration in the thermal barrier assembly.
Attempts to increase the adhesion of the adhesive composition to the interior channel surface includes mechanically roughening the surface of the channel using methods such as abrading, scratching, lancing, sand blasting and scraping. Often the aesthetics of the assembly are sacrificed during these processes. In addition, these mechanical roughening techniques normally are conducted in a separate, off-line operation. Other methods that have been used in an effort to increase adhesion include chemical treatments such as solvent bonding and chemical etching.